Polyetherimide ester elastomers comprised of the reaction products of (a) a low molecular weight diol, (b) a dicarboxylic acid, (c) a high molecular weight poly(oxy alkylene)diamine, and (d) a tricarboxylic acid or its derivative are known and are described in U.S. Pat. Nos. 4,544,734 and 4,556,705 to McCready and in U.S. Pat. No. 4,556,688 to McCready et al. These polyetherimide esters exhibit excellent stress-strain properties, low tensile set, high melting temperatures and/or excellent strength/toughness characteristics as well as superior flexibility, which properties render said polyetherimide esters especially suitable for molding and extrusion applications.
However, these polyetherimide esters, in unmodified form, do not have an exceptional melt strength. In addition, the heat stability of these esters can be improved. It would best be very advantageous if polyetherimide esters could be provided which exhibit improved melt strength and, in addition, improved heat stability.
It has now been discovered that these polyetherimide ester polymers can obtain an improved melt strength and a resultant improved blow moldability when they are admixed with a multifunctional epoxy compound. Optionally, the heat stability of the above mentioned polyetherimide ester elastomer can be improved by admixing the elastomer with a multifunctional epoxy compound, a hindered phenol and a thio ester.